As the use of computers and the Internet have proliferated, so too has the use of application programs. A multitude of application programs exist for performing tasks such as word processing, accounting, graphic art, etc. In addition, there are numerous platforms or operating systems on which these application programs operate. For example, Apple® Macintosh® machines may use the Mac OS X operating system and support Microsoft's Word X for word processing, whereas Compaq® machines may use the Microsoft Windows operating system and support Microsoft word for word processing.
There are application programs that enable a user to provide a note (e.g., an annotation, a drawing, etc.) in another application program (e.g., a word processing document). The note is displayed over part of the text and images of the word processing document. (see U.S. Pat. No. 5,559,942 issued to Gough et al. of Apple Computer Inc., of Cupertino Calif.). The note provides a useful means for a user to annotate the underlying word processing document and is displayed using an anchor object in the word processing document.
The notes described in U.S. Pat. No. 5,559,942 are not separable from the document in which they appear. Moreover, a document that includes the notes created on a machine with a particular operating system may not be viewed on another machine with a different operating system. What is needed, therefore, is a method and apparatus to mark-up an electronic document (i.e., a second electronic document) that is superimposed on a first electronic document (e.g., a word processing document) keeping the first electronic document unchanged. The second electronic document is optionally viewed concurrently with the first electronic document, and the second electronic document is capable of being viewed or modified using different application programs so long as the different application programs process the format used by the second electronic document. The second electronic document is saved as a separate document independent of the first electronic document. Furthermore, the application programs that permit the second electronic document to be viewed or modified may be operational on machines that use the same operating system as the machine that created the second electronic document. Alternately, the application programs that permit the second electronic document to be viewed or modified may be operational on machines that use a different operating system so long as the application programs process the format of the second electronic document.